Act IThe Royal Palace at Memphis; Egypt and
Ethiopia are at war. Radames and Ramfis enter. They discuss the rumour that
the Ethiopians are planning a new attack and Ramfis discloses that
the priesthood has consulted the goddess Isis as to who should lead
Egypt’s forces. He looks meaningfully at Radames, but names no-one. Alone,
Radames muses on forthcoming glory and the chance that it may enable him to
marry Aida, a beautiful Ethiopian slave girl. Amneris enters and asks about
his evident happiness. She hints at a loved one in Memphis and he
looks away. She is consumed by jealousy because she loves Radames herself. Aida
enters and Amneris feigns kindness to her, while noticing that Aida and Radames
cannot look at one another. The Pharaoh enters with the court. A
messenger brings news of the Ethiopians’ coming attack, led by King
Amonasro who, unknown to everyone, is Aida’s father. There is a call for
war. Radames is named general and given the standard by Amneris.
The battle hymn concludes and the court departs. Aida is left alone
in confusion, unable to pray for Radames’ victory, yet, in her love
for him, wishing his safe return. At the Temple of Vulcan a ritual
is in progress. Radames is led in by Ramfis and consecrated with his
weapons at the high altar. Both invoke the blessing of the god
Ptah for the campaign.

Act II In her apartments, Amneris awaiting
the return of Radames, the man she loves and who has been victorious,
and is entertained by dancers. Aida comes in with Amneris’ crown. Feigning
kindness once again, Amneris hints that she knows Aida is in love with an
Egyptian. She then casually mentions that Radames has been killed and Aida’s
outburst reveals to her the truth. Admitting that she lied, Amneris cruelly
threatens Aida who – after a moment’s defiance – vainly begs for
forgiveness. Outside, the sound of the returning warriors is heard.
In Thebes, the Pharaoh, Amneris, priests and courtiers await
the arrival of Radames and his victorious army. At the end of
a long procession Radames enters and is crowned victor by Amneris while
the Pharaoh proclaims him the country’s saviour. Asked to name
a favour, Radames requests the Ethiopian slaves be brought in. Aida
recognises her father, but Amonasro whispers to her not to betray his true
identity. To the Pharaoh he describes how he and his comrades fought
valiantly but how their King was killed in battle. He pleads for mercy and
Radames asks that the captured Ethiopians be set free. Ramfis opposes him,
but eventually consents so long as the “spokesman” is kept under custody.
The Pharaoh agrees, and then promises Radames the hand of his daughter
in marriage. Radames will reign after him. Only Radames and Aida privately
voice sorrow at the royal decree.

Act IIIAt night on the banks of the Nile
the sounds of chanting can be heard coming from the Temple of Isis.
Amneris arrives with Ramfis to spend time before her wedding in prayer and
they go into the Temple. Aida enters to meet Radames in secret. As she
cannot be his, she thinks of drowning herself in the Nile. But
Amonasro appears having eluded his guard, and tells Aida that she must help her
country in a new uprising. She must find out from Radames
the route the Egyptian army plans to take against them. At first she
refuses but, eventually worn down by her father, she agrees. Amonasro hides as
Radames enters, believing that if he is successful in battle a second
time the Pharaoh will not oppose their marriage. Aida tells him that their
only fortune together is in flight to her homeland. Eventually he yields to
her, and she casually asks which route the army will take to Ethiopia. As
he tells her, Amonasro steps out of the shadows, and Radames is horrified
to see what he has done. Both Amonasro and Aida try to persuade him to come with
them, but Amneris comes out of the Temple followed by Ramfis. Amonasro
tries to stab Amneris but Radames protects her. As Aida and Amonasro escape
Radames surrenders to the guards Ramfis has called.

Act IV In a hall in the Palace,
above the underground Chamber of Justice, Amneris waits alone, torn between
her love and a desire for vengeance. She sends for Radames and offers to
secure a royal pardon if he will give up Aida, who has made good her
escape. Radames refuses and Amneris sends him to his trial. Alone again she
hears the charges against him read out and then the sentence of death.
As Radames is led up she curses the priests’ cruelty.
In the Temple tomb in which Radames has been sentenced to
a live burial he awaits death. The last stone has been put
in place when he hears a noise beside him. It is Aida who has stolen
into the tomb to die with him. They bid each other farewell while above,
in the Temple, priestesses chant and Amneris prays to Isis that
Radames’ soul may rest in peace.